Resolving pronoun ambiguity in voice queries

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for resolving ambiguity in received voice queries. An original voice query is received following one or more earlier voice queries, wherein the original voice query includes a pronoun or phrase. In one implementation, a plurality of acoustic parameters is identified for one or more words in the original voice query. A concept represented by the pronoun is identified based on the plurality of acoustic parameters, wherein the concept is associated with a particular query of the one or more earlier queries. The concept is associated with the pronoun. Alternatively, a concept may be associated with a phrase by using grammatical analysis of the query to relate the phrase to a concept derived from a prior query.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/774,082, filed Feb. 22, 2013, which claims the benefit of U.S.Provisional Application Nos. 61/654,742 filed Jun. 1, 2012 and61/654,518 filed Jun. 1, 2012, each of which are incorporated herein intheir entirety by reference.

FIELD

This specification describes technologies related to providinginformation in response to user queries.

BACKGROUND

A mobile device, such as a smartphone or another portable computingapparatus, may run a search engine that receives queries, for example,from one or more users and returns query results responsive to thequeries. For example, the search engine run by the mobile device canidentify documents responsive to a query, generate query results withinformation about the documents, and provide the query results inresponse to the query. Other types of query results, for example, directanswers to questions posed by the user, or a summary of informationresponsive to the user's query, can also be provided. The usefulness ofa search engine for a mobile device can depend on its ability to providesatisfactory query results.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in methods that include the actionsof receiving an original voice query, identifying a plurality ofacoustic parameters associated with a pronoun included in the originalvoice query, identifying a concept represented by the pronoun based onthe plurality of acoustic parameters, such that the concept is derivedfrom a particular query of one or more earlier queries received beforereceiving the original voice query, and associating the concept with thepronoun.

Another innovative aspect of the subject matter described in thisspecification can be embodied in methods that include receiving anoriginal voice query after having received one or more earlier voicequeries, wherein the original voice query includes a phrase that refersto a concept from one of the earlier voice queries, analyzing thegrammatical structure of the original query to extract the phrase thatrefers to a concept from one of the earlier voice queries, extracting adeterminer word from the phrase, identify an object word of thedeterminer word from the phrase, finding a set of hypernyms for theobject word, identifying a concept represented by the phrase, whereinthe concept is derived from a particular query of the one or moreearlier queries, by comparing the one or more earlier queries to thephrase and the set of hypernyms, and associating the concept with thephrase.

Other embodiments of this aspect include corresponding computer systems,apparatus, and computer programs recorded on one or more computerstorage devices, each configured to perform the actions of the methods.A system of one or more computers can be configured to performparticular operations or actions by virtue of having software, firmware,hardware, or a combination of them installed on the system that inoperation causes or cause the system to perform the actions. One or morecomputer programs can be configured to perform particular operations oractions by virtue of including instructions that, when executed by dataprocessing apparatus, cause the apparatus to perform the actions.

The foregoing and other implementations can each optionally include oneor more of the following features, alone or in combination. Inparticular, one implementation may include all the following features incombination. The methods can further include the actions of modifyingthe original voice query to include the concept and presenting one ormore query results that are responsive to the modified original voicequery. In an implementation, the acoustic parameters may include two ormore of volume, pitch, frequency, duration between each spoken word, andspoken duration. The particular query may be a most recent voice queryof the one or more earlier voice queries. In an implementation,identifying the concept represented by the pronoun based on theplurality of acoustic parameters may include determining that theplurality of acoustic parameters for the pronoun indicates that thepronoun was stressed. For example, determining that the plurality ofacoustic parameters for the pronoun indicates that the pronoun wasstressed may include determining a stress score for the pronoun based onthe plurality of acoustic parameters and determining that the stressscore satisfies a predetermined threshold.

Alternatively, identifying the concept represented by the pronoun basedon the plurality of acoustic parameters may include determining that theplurality of acoustic parameters for the pronoun indicates that thepronoun was not stressed. For example, determining that the plurality ofacoustic parameters for the pronoun indicates that the pronoun was notstressed may include determining a stress score for the pronoun based onthe plurality of acoustic parameters and determining that the stressscore does not satisfy a predetermined threshold.

The subject matter described in this specification can be implemented inparticular embodiments so as to realize one or more of the followingadvantages. The performance of existing search engines used by mobiledevices can be improved. For example, pronouns in voice queries can bedisambiguated. Query results based on the disambiguated pronoun can bereturned to the user. By doing this, search engines can focus on findingresults that are more relevant to what a searching user would like toreceive.

The details of one or more embodiments of the subject matter of thisspecification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example search system for providing query resultsresponsive to submitted queries.

FIGS. 2A and 2B illustrate examples of resolving pronoun ambiguity toprovide query results responsive to submitted queries.

FIG. 3 illustrates an example pronoun resolution system.

FIG. 4 illustrates an example method of associating a concept with apronoun based on acoustic parameters and prior queries.

FIG. 5 illustrates an example method for associating a concept with apronoun based on grammatical analysis.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 illustrates an example search system 112 for providing queryresults responsive to submitted queries as can be implemented in aninternet, an intranet, or another client and server environment. Thesearch system 112 is an example of an information retrieval system inwhich the systems, components, and techniques described below can beimplemented. However, it will be noted that while FIG. 1 presents animplementation that is presented based on a client-server architecture,other network architectures such as a peer-to-peer architecture may beused appropriately.

A user 102 can interact with the search system 112 through a clientdevice 104. For example, the client 104 can be a computer coupled to thesearch system 112 through a local area network (LAN) or wide areanetwork (WAN), e.g., the Internet. In some implementations, the searchsystem 112 and the client device 104 can be one machine. For example, auser can install a desktop search application on the client device 104.The client device 104 will generally include a random access memory(RAM) 106 and a processor 108. In such an implementation, thefunctionality is carried out locally at one machine.

A user 102 can submit a query 110 to search system 112. The query shouldinclude information that specifies what information user 102 would likesearch system 112 to find. For example, the query may include keywords,as well as additional search query modifiers such as Boolean operators,wildcards, and filters.

The query 110 can be submitted to search engine 116 by differentmethods. For example, user 102 can submit the query by speaking thequery 110. An audio input device associated with client device 104 willdetect the query 110 and transmit the query 110 through a network tosearch system 112. In such a method, the audio input is recognized. Forexample, keywords may be recognized from the audio input, or othersearch query modifiers as discussed above may be recognized from anaudio query 110. Other methods of submitting queries to search engine116 can also be performed. For example, user 102 can interact with auser interface associated with client device 104 to submit the query110. The user interface can be any input device (e.g., keyboard, mouse,touch display device) that allows user 102 to enter query 110 into agraphical user interface of search system 112. For example, user 102 maytype a query 110 into a search box. However, user 102 may also enterinformation about what they would like to search for, for example, byusing a mouse or touch display device to enter part of the query throughcontrols such as drop-down menus, check boxes, radio buttons, and othergraphical controls that help specify query 110.

The search system 112 can be implemented as, for example, computerprograms running on one or more computers in one or more locations thatare coupled to each other through a network. For example, in oneimplementation, the search system 112 includes an index database 114, asearch engine 116, and a pronoun resolution system 122. However, otherimplementations may include different constituent parts that performsimilar functionality. The search system 112 responds to the query 110by generating query results 124, which one or more query results 124 canbe transmitted through the network to the client device 104 in a formthat can be presented to the user 102.

When a voice query containing a pronoun is received by the search system112, the pronoun resolution system 122 resolves the ambiguous pronoun byassociating a concept with the pronoun based on the acoustic parametersof the received voice query, as described in more detail below withreference to FIG. 4. A concept can be a noun or subject that isreferenced by the ambiguous pronoun. The voice query 110 is converted totext and modified to include the concept and sent to the search engine116. Because the converted query includes the concept, it is no longerambiguous and search engine 116 can work normally. Examples of how thisprocess works are presented, below.

While the pronoun resolution system 122 is depicted as a componentwithin search system 112, the pronoun resolution system 122 may also beimplemented as, for example, computer programs running on one or morecomputers outside search system 112 and communicatively coupled withsearch system 112 through a network. The pronoun resolution system 122transmits the resolved query to search engine 116. In oneimplementation, pronoun resolution system 122 uses information aboutacoustic parameters of query 110 and previous queries to disambiguatethe pronoun in query 110. In another implementation, information aboutthe grammatical structure of query 110 and previous queries todisambiguate the pronoun in query 110. In either case, the taskperformed by pronoun resolution system 122 is accomplished such that itcan use information to provide clues about what the pronoun in query 110actually corresponds to, then including that in query 110 beforeobtaining query results 124 by search engine 116, as will now bediscussed.

Search engine 116 identifies resources that match the query. The searchengine 116 can be, for example, an Internet search engine that takesaction or identifies answers based on user queries, a question andanswer system that provides direct answers to questions posed by theuser, or another system that processes user requests. Essentially, thedefining quality of search engine 116 is that it receives query 110 andprovides query results 124 that are responsive in some way to query 110.

For example, the search engine 116 may also identify a particular“snippet” or section of one or more of the resources that are relevantto the query. For example to aid in such a task, search engine 116 willgenerally include an indexing engine 118 that indexes resources, e.g.,web pages, images, or news articles on the Internet, found in a corpus,e.g., a collection or repository of content, an index database 114 thatstores the index information, and a ranking engine 120, or othersoftware, to rank the resources that match the query 110. While otherarchitectures for search engine 116 may be used, a search engine 116that uses index database 114 in combination with indexing engine 118,and ranking engine 120 will be able to take query 110 and provideappropriate query results 124.

The ranking engine 120 ranks query results that are responsive to thequery by determining one or more signals for the query result and thequery pair, determining a score for each query result, and then rankingthe query results based on the received scores. Examples of signalsinclude signals indicating relevance of the resource to the query andsignals indicating the quality of the resource. In general, a signal isinformation that is useful in providing scoring information that can beused to provide meaningful improvement of the ranking process. Variousapproaches exist to obtain signal information, use the signalinformation to generate scores, and rank query results based on thescores. Additionally, user 102 may be able to control parameters ofranking engine 120 to help provide ranking engine 120 with additionalinformation, as well as the query itself, that may indicate whichresults should be ranked the highest or filtered out. For example, user102 may control the ranking by asking ranking engine 120 to only includequery results from within the last week.

FIGS. 2A and 2B illustrate examples of resolving pronoun ambiguity toprovide query results responsive to submitted queries as implemented bythe search system described above with reference to FIG. 1. FIGS. 2A and2B are presented as an example sequence of events that may occur duringa typical interaction between a mobile device and a search engine inwhich the user incorporates a pronoun into his or her query.

In FIG. 2A, user 202 asks “Who invented the telephone?” 210. User device204 receives the voice query 210 and responds to voice query 210 byanswering, as query result, “Alexander Graham Bell” 212. Subsequently,user 202 asks “Who was Alexander Graham Bell's father?” 214. User device204 receives the voice query 214 and responds to voice query 214 byanswering “Alexander Melville Bell” 216. Subsequently, user 202 asks“What is HIS birthday?” 218. User device 204 receives voice query 218.The system identifies the term “his” in voice query 218 as a pronoun anddetermines that “his” was stressed when spoken by user 202. Thisdetermination may be made on the basis of acoustic parameters associatedwith the way user 202 pronounced the word “HIS.” For example, theseacoustic parameters may include information about various parts of thevoice query, including parameters such as volume, pitch, frequency,duration between each spoken words, and spoken duration of words orphrases. Analyzing these acoustic parameters may allow implementationsto calculate a stress score for parts of what is said. Implementationsmay calculate a stress score for the pronoun based on the acousticparameters. The determination of the stress score may also be based oncomparing acoustic parameters for the pronoun to acoustic parameters forother parts of the voice query. By comparing the stress score for thepronoun to a threshold, an implementation may determine that the stressscore indicates that the pronoun is stressed or not.

In the case of FIG. 2A, the implementation determines that “his” wasstressed. Based on the determination that “his” was stressed, the systemassociates “his” with the concept of the immediately preceding query,Alexander Melville Bell rather than the original query, “AlexanderGraham Bell”. Based on this association, the user device 204 responds tovoice query 218 by answering “Alexander Melville Bell's birthday is Mar.1, 1819” 220.

In FIG. 2B, user 202 asks “Who invented the telephone?” 260. User device204 receives the voice query 260 and responds to voice query 260 byanswering “Alexander Graham Bell” 262. Subsequently, user 202 asks “Whowas Alexander Graham Bell's father?” 264. User device 204 receives thevoice query 264 and responds to voice query 264 by answering “AlexanderMelville Bell” 266. Subsequently, user 202 asks “What is his birthday?”268. User device 204 receives voice query 268. The system identifies theterm “his” in voice query 268 as a pronoun and determines that “his” wasnot stressed when spoken by user 202. Once again, this determination ismade based on acoustic parameters associated with the way the pronoun,“his,” is pronounced. In this case, the acoustic parameters indicatethat “his” is not stressed by user 202, so the pronoun refers to theanswer to the original query, “Alexander Graham Bell”, rather than theanswer to the follow-up query, “Alexander Melville Bell.” Based on thedetermination that “his” was not stressed, the system associates “his”with the concept of the original voice query, Alexander Graham Bell.Based on this association, the user device 204 responds to voice query268 by answering “Alexander Graham Bell's birthday is Mar. 3, 1847” 270.

FIGS. 2A and 2B illustrate user device 204 responding to user 202 voicequeries by presenting answers audibly by an audio output deviceassociated with user device, such as speaker 208, and displaying answerson active display screen 206. Alternatively, the display screen 206 maybe in a low-power or no-power state. In some implementations, theanswers may be presented either only audibly or only visually. Thesefigures illustrate that an implementation can use acoustic parameterswhen analyzing a query, such as by comparing acoustic parameters for apronoun to acoustic parameters for other parts of a query, to determinewhether the pronoun is stressed or whether there are other cluesincluded in how the query is articulated that reveal the intention ofuser 202 with respect to a pronoun. For example, if a pronoun isstressed, it may indicate that it refers to a concept from animmediately preceding query, while a pronoun that is not stress mayrefer to a concept from a query that occurred earlier in a series ofreceived queries.

FIG. 3 illustrates an example pronoun resolution system 302. The examplepronoun resolution system 302 is an example of the pronoun resolutionsystem 122 described above with reference to FIG. 1. Otherimplementations may use other architectures to provide similarfunctionality.

The pronoun resolution system 302 includes a text conversion module 314,an acoustic parameters module 308 within text conversion module 314, astress determination module 310, and a concept association module 312.The pronoun resolution system 302 receives a query 304 containing anambiguous pronoun and outputs a resolved query 306 containing a conceptthat disambiguates the pronoun.

The text conversion module 314 receives the voice query 304 and convertsvoice query 304 into text, for example, using conventional voice to texttranslation techniques. At the same time that text conversion module 314converts voice query 304 to text, acoustic parameters module 308identifies acoustic parameters for one or more words in voice query 304.The acoustic parameters can include the volume, frequency, and pitch ofthe spoken words in voice query 304. The acoustic parameters can alsoinclude the time duration between the spoken words and the time durationfor the spoken words in voice query 304. In some implementations, atleast two different acoustic parameters are identified for the one ormore words in voice query 304.

Acoustic parameters module 308 receives voice query 304 in an audiosignal waveform from a microphone associated with the user device thatdetects the voice query 304. The audio signal waveform is an electricalsignal that represents the mechanical sound waves produced by the userwhen speaking voice query 304. Acoustic parameters module 308 analyzesthe audio signal waveform that corresponds to voice query 304 withtechniques that analyze audio signals, for example, conventionaltechniques such as Fast Fourier Transforms (FFTs). From the analysis,the acoustic parameters describing the voice query are identified. Forexample, the volume of the audio signal waveform can be determined fromthe amplitudes of the audio signal waveform. The frequency can bedetermined from the number of oscillations in the audio signal waveformin a period of time. The pitch can be determined from the frequency thatdescribes the audio signal waveform. Other acoustic parameters can bedetermined by performing other appropriate mathematical analysis of theaudio signal waveform to provide relevant data for the audio signalwaveform.

In some implementations, acoustic parameters for each word in the voicequery 304 are identified. For example, the volume for a particular wordcan be determined from the peak amplitude of the section of the waveformthat corresponds to the particular word. Alternatively, the volume canbe an average of the amplitudes in the section of the waveform thatcorresponds to the particular word. The frequency for a particular wordcan be determined as the maximum or minimum frequency measurement thatcorresponds to the section of the waveform that corresponds to theparticular word. Alternatively, the frequency can be determined as anaverage of the discrete frequencies measured from the section of theaudio signal waveform that corresponds to the particular word.Additionally, the time duration between the particular word and the wordimmediately before or after the particular word in voice query 304 canbe identified from the section of audio signal waveform that is betweenthe section corresponding to the particular word and the sectionscorresponding to the word immediately before or after the particularword. Also, the time duration for the particular word can be identifiedfrom the section of the audio signal waveform that corresponds to theparticular word. The identified acoustic parameters for each word in thevoice query 304 are associated with the text of the corresponding word.The text of voice query 304 and the associated acoustic parameters foreach word in the text are transmitted to stress determination module310. One advantage of obtaining acoustic parameters for each word isthat it can allow comparison of acoustic parameters between differentwords within voice query 304.

The stress determination module 310 determines a stress score based onthe parameters. The stress score indicates how likely it is that thepronoun in voice query 304 was stressed by the speaker. For example, thestress determination module 310 can provide the acoustic parametersdetermined by acoustic parameters module 308 to a machine learningsystem that has been trained to generate stress scores in a way thatprovides representative stress scores based on analyzing acousticparameters. The provided acoustic parameters can be acoustic parametersidentified for just the pronoun or acoustic parameters identified for acombination of words in voice query 304. The machine learning systemapplies weights learned during the training process to the acousticparameters and outputs a stress score.

In some implementations, the acoustic parameters for the pronoun areabsolute measures of the acoustic parameters for the pronoun. Theabsolute measures are determined directly from the section of thewaveform that corresponds to the pronoun as described above. In otherimplementations, the acoustic parameters for the pronoun are relativemeasures of the acoustic parameters for the pronoun. The relativemeasures are derived from the acoustic parameters for the pronoun andthe acoustic parameters for the other words in verbal query 304, asidentified from their respective sections of the waveform as describedabove. The relative measures can be a ratio between the acousticparameters for the pronoun and the acoustic parameters for the otherwords in voice query 304.

For example, if the absolute measure for the volume of the pronoun is 80dB and the average volume for the other words in voice query 304 is 60db, the ratio of the volumes is 1.33. This relative volume measure forthe pronoun indicates that the volume of the pronoun is 33% greater thanthe volume of the rest of voice query 304. Alternatively, the relativemeasures can be a difference between the acoustic parameters for thepronoun and the acoustic parameters for the other words in voice query304. For example, if the absolute measure for the time duration of thepronoun is 80 ms and the average time duration of the other words invoice query 304 is 50 ms, the difference in the time duration is 30 ms.This relative time duration measure for the pronoun indicates that thetime duration of the pronoun is 30 ms more than the average timeduration for the words in voice query 304. Alternatively, the relativemeasures of the acoustic parameters for the pronoun can be relative tothe acoustic parameters for only the words that immediately proceed andfollow the pronoun.

Concept association module 312 receives the stress score output bystress determination module 310. Based on the stress score, conceptassociation module 312 disambiguates the pronoun in voice query 304 byidentifying a concept represented by the pronoun and associating theconcept with the pronoun, as described in more detail below withreference to FIG. 4. A resolved query 306 is generated from theidentified concept and voice query. In some implementations, the voicequery 304 can be modified to include the identified concept. Forexample, the pronoun in voice query 304 can be replaced with theidentified concept. Alternatively, the concept can be added to voicequery 304. In either case, once the pronoun has been integrated intovoice query 304, it is available when voice query 304 is used as part ofa search and hence the search process has available disambiguatedinformation that allows it to search for an explicit concept that is ofspecific interest rather than trying to find an ambiguous pronoun.

FIG. 4 illustrates an example method of associating a concept with apronoun. For convenience, the example method 400 will be described inreference to a system that performs method 400. The system can be, forexample, the pronoun resolution system described above with reference toFIG. 1 and FIG. 3. In some implementations, the system can be one ormore computers.

In stage 410, the system receives an original voice query. As previouslydiscussed, the receipt of the original voice query may occur at clientdevice 104. For example, user 102 may articulate a voice query 304 thatis received by a microphone at client device 104 by a microphone.Subsequently, text conversion module 314 may convert voice query 304into a transcribed query for use in the search process.

In stage 420, the system identifies a plurality of acoustic parametersassociated with a pronoun included in the original voice query. Forexample, after voice query 304 has been transcribed by text conversionmodule 314, acoustic parameters module 308 may operate as discussedabove to establish acoustic parameters for query 304. The specifics ofhow acoustic parameters are obtained and used have been discussed ingreater detail in the discussion of FIG. 3, above.

In stage 430, the system identifies a concept represented by the pronounbased on the plurality of acoustic parameters, wherein the concept isderived from a particular query of one or more earlier queries receivedbefore receiving the original voice query. For example, pronounresolution system 302 may provide a transcribed version of query 304 andinformation about associated acoustic parameters to stress determinationmodule 310. Based on results from stress determination module 310, aswell as other analysis, concept association module 312 may operate so asto ascertain which concept is most relevant to the pronoun. Examples ofhow this process may occur have been presented above in the discussionof FIGS. 2A-2B.

In stage 440, the system associates the concept with the pronoun. Asdiscussed above, this stage occurs such that concept association module312 indicates that the pronoun in query 304 actually refers to aspecific concept based on analysis of the acoustic parameters of query304 as well as information such as concepts from other queries.

The method may also include certain optional stages.

In stage 450, the system modifies the query to include the concept. Thisstage is an extension of stage 440 in that stage 440 indicates thatthere is a relationship between the pronoun and the concept. In stage450, the concept is actually integrated into the query itself. In thiscase, what occurs is that either the concept replaces the pronoun, orthe concept is added as an alternative to the pronoun. For example,suppose that an implementation receives the query, “What is HISbirthday?” and establishes that “HIS” stands for “Alexander GrahamBell.” In this stage, concept association module 312 may produce areceived query that is either “What is Alexander Graham Bell'sbirthday?” or alternatively, “What is (HIS or Alexander Graham Bell's)birthday?” Here, one key factor is that the concept that is associatedwith the pronoun is now an actual part of the query.

In stage 460, the system presents results based on the query. Generally,search engine 116 receives received query 306, which now includesinformation about the concept such that received query 306 is no longerambiguous. Thus, search engine 116 can search based on received query306. That search produces query results 124, which may be provided byclient device 104 to user 102. The system can cause the query results tobe presented on a display screen associated with a user device or causesound describing the one or more query results to be presented through aspeaker associated with user device.

Other implementations include additional and alternative featuresrelative to the implementation presented in FIG. 4. In someimplementations, the system can receive multiple voice queries beforereceiving the original voice query. The system can be, for example, anInternet search engine, or other system, that takes action or identifiesanswers based on the voice queries or a question and answer system thatprovides direct answers to the voice queries. The system can respond tothe prior queries by presenting query results or answers in response tothe prior queries. A concept can be derived for each query and queryresult pair. The concept can be a person, place, or thing.

For example, before receiving the original voice query, the user canfirst present a voice query, “Who invented the telephone?” In response,the system provides the answer, “Alexander Graham Bell invented thetelephone.” From the query “Who invented the telephone?” and the answer“Alexander Graham Bell invented the telephone,” the system can derive“Alexander Graham Bell” as the concept for the query. Subsequently, theuser can present a follow-up voice query, “Who was Alexander GrahamBell's father?” In response, the system provides the answer, “AlexanderGraham Bell's father is Alexander Melville Bell.” From the query “Whowas Alexander Graham Bell's father?” and the answer “Alexander GrahamBell's father is Alexander Melville Bell,” the system can derive“Alexander Melville Bell” as the concept for the query. The system thenreceives the original voice query containing a pronoun. The pronoun inthe received original query references a derived concept of one of thequeries received by the system before receiving the original voicequery.

In some implementations, the system can receive a single voice querybefore receiving the original voice query. The system can respond to thequery by presenting a query result or answer in response to the query. Aconcept can be derived for both the query and query result or answer.For example, before receiving the original voice query, the user canpresent a voice query, “Who is Alexander Graham Bell's father?” Thesystem can derive “Alexander Graham Bell” as the concept for the query.In response to the query, the system provides the answer, “AlexanderMelville Bell.” The system can derive “Alexander Melville Bell” as theconcept for the answer. The system then receives the original voicequery containing a pronoun. The pronoun in the received original queryreferences a derived concept of either the query received before theoriginal query or the answer for the query received before the originalquery.

The identified concept is associated with one of the earlier voicequeries received before the original voice query or answers for theearlier voice queries as described above. Analysis of the original voicequery indicates a degree of stress the user placed on the pronoun whenspeaking the original voice query. If the stress score satisfies apredetermined threshold, then it is determined that the pronoun wasstressed. In response to determining that the pronoun was stressed, thesystem identifies the most recently derived concept as the conceptrepresented by the pronoun. For example, the identified concept can bethe concept derived from the most recent of the one or more earlierqueries. Alternatively, the identified concept can be the most recentlyderived concept for a query and query answer pair for a query receivedby the system before the original voice query. The identified conceptcan be the concept derived from the query answer. If the stress scoredoes not satisfy a predetermined threshold, then it is determined thatpronoun was not stressed. In response to determining that the pronounwas not stressed, the system identifies a concept derived before themost recently derived concept as the concept represented by the pronoun.For example, the identified concept can be the concept derived from aquery that preceded the most recent of the one or more earlier queries.Alternatively, the identified concept can be the earlier derived conceptfor a query and query answer pair for a query received by the systembefore the original query. The identified concept can be the conceptderived from the query.

In some implementations, the system identifies a concept represented bythe pronoun based on the gender that the pronoun references.Gender-specific pronouns can be used to help identify the concept. Forexample, the user can present a voice query, “Who is Alexander GrahamBell's mother?” The system can derive “Alexander Graham Bell” as theconcept for the query. In response to the query, the system provides theanswer, “Eliza Grace Symonds Bell.” The system can derive “Eliza GraceSymonds Bell” as the concept for the answer. The system then receivesthe original voice query, “When is her birthday?” The system canrecognize that the “her” in the original voice query is afemale-specific pronoun and identify a female related concept of thepreviously derived concepts as the concept represented by the pronoun.The system can determine that of the identified concepts, only “ElizaGrace Symonds Bell” is a female related concept and identifies “ElizaGrace Symonds Bell” as the concept represented by the pronoun. Thesystem can determine the gender of a concept using a trained machinelearning system. The concept can be provided to the trained machinelearning system to output a gender score that represents a genderdetermination for the concept.

In some implementations, the system identifies a concept represented bythe pronoun based on both the gender that the pronoun references and thestress determination for the pronoun. For example, if both the stressscore and the gender score for the pronoun indicate that the pronounrefers to the same concept, then the system identifies that concept asthe concept represented by the pronoun. If the stress score and thegender score for the pronoun indicate that the pronoun refers todifferent concepts, the system makes a determination on which score torely on. For example, the system can choose to rely on the score withthe greater confidence level. Alternatively, the system can always relyon just the stress score or just the gender score when the two scoresindicate different concepts for the pronoun.

An implementation may also use machine learning to train stressdetermination module 310 to improve the results of stress scoring. Thesystem receives data comprising a plurality of voice queries containingpronouns, stress values for each of the plurality of voice queries, andacoustic parameters for each of the plurality of voice queries. Forexample, the data can be collected by presenting the voice queries toone or more human raters. The human raters can provide stress values foreach of the presented voice queries. The stress value indicates a levelof emphasis placed on the pronoun in the presented voice queries asdetermined by the human raters. In some implementations, the providedstress values range in value from −1 to 1. Various ranges canalternatively be used. In other implementations, the provided stressvalues can be 0 or 1, indicating that the pronoun is either stressed ornot stressed. The system can identify the plurality of acousticparameters for one or more words in the voice queries as described abovein reference to FIG. 3. The acoustic parameters can include, forexample, at least two of volume, pitch, frequency, duration between eachspoken word, and spoken duration. Other acoustic parameters can also beused.

Alternatively, the data can be collected by having one or more humanraters speak the plurality of voice queries. The system can identify theacoustic parameters of each spoken voice query, and ask the human raterto also provide a stress value indicating the level of stress the humanrater placed on the pronoun in the spoken voice query.

The system trains a machine learning system using the received data, forexample, using conventional techniques. For example, the data can betransformed into a plurality of feature vectors for each voice query.Each feature vector for a voice query represents the data describing theacoustic parameters for the voice query. A learning algorithm analyzesthe training data comprising of the feature vectors and stress value foreach voice query in the machine learning system to determine theappropriate weights for each of the acoustic parameters.

The machine learning system described above is trained to output stressscores that represent a level of stress placed on a pronoun in a voicequery based on the acoustic parameters of the voice query. This stressscore is then used by the system to identify a concept represented bythe pronoun, as described above in reference to FIG. 4.

FIG. 5 illustrates an example method for associating a concept with apronoun based on grammatical analysis.

Stage 510 includes receiving an original voice query after havingreceived one or more earlier voice queries, wherein the original voicequery includes a phrase that refers to a concept from one of the earliervoice queries. This stage is similar to stage 410 in that user 102provides client device 104 with audio that may be transcribed by textconversion module 314 into a textual query. However, in stage 510 thequery includes a phrase that refers to a concept. For example, user 102might have previously issued a query to which the answer was,“Laphroaig.” The original voice query might be a follow up query,asking, “What drinks can I make with that tasty scotch?”

Here “that tasty scotch” is an entire phrase that refers to “Laphroaig,”a particular brand of scotch. However, “that tasty scotch” is stateful,in that it only makes sense with reference to “Laphroaig” from theprevious query. The implementation of FIG. 5 operates so as to identify“that tasty scotch” and replace it with “Laphroaig,” thereby renderingthe query stateless.

Stage 520 includes analyzing the grammatical structure of the originalquery to extract the phrase that refers to a concept from one of theearlier voice queries. For example, this stage may be performed byconcept association module 312. Analyzing the grammatical structure mayestablish which phrase is a concept by using part-of-speech tagging andidentifying dependency information. For example, “what drinks can I makewith that tasty scotch” might ascertain parts of speech and further usethis information to establish that the phrase to clarify is “that tastyscotch.”

Stage 530 includes extracting a determiner word from the phrase. Forexample, this stage may be performed by concept association module 312.Here, “that” is the relevant determiner word.

Stage 540 includes identifying an object word of the determiner wordfrom the phrase. For example, this stage may be performed by conceptassociation module 312. Here, “scotch” is the object of that.

Stage 550 includes finding a set of hypernyms for the object word. Forexample, this stage may be performed by concept association module 312.For example, this set might determine that scotch “is-a” “liquor”,“spirit”, “whiskey”, “drink” and so forth. For example, this stage maybe facilitated using an appropriate lookup table.

Stage 560 includes identifying a concept represented by the phrase,wherein the concept is derived from a particular query of the one ormore earlier queries, by comparing the one or more earlier queries tothe phrase and the set of hypernyms. For example, this stage may beperformed by concept association module 312. Essentially, this stageincludes using a variety of heuristics to establish how similar conceptsfrom previous queries are to the phase. In this example, “Laphroaig” isan answer to an earlier query. For example, user 102 might have asked,“What is my favorite alcoholic beverage?” and search engine 116 may haveretrieved “Laphroaig” as the answer. Since “scotch” is the object of“that”, and is further modified by “tasty,” an implementation may beable to identify that “scotch,” especially “tasty scotch,” falls intomany overlapping categories with “Laphroaig.” For example, both mighthave as a hypernym “spirit.” Various heuristics may be used todiscriminate between specific candidate concepts, when multipleplausible candidate concepts are available. For example, heuristics mayinclude factors such as term distance, numbers of shared hypernyms,longest terms, or other factors that may indicate a likelihood that aconcept is likely to be a helpful replacement for the phrase.

Stage 570 includes associating the concept with the phrase. This stageis carried out in a manner similar to stage 440. It may be noted thatstage 570 may be followed appropriately by incorporating the conceptinto the query and searching based on the query by stages that aresimilar to stage 450 and 460.

Embodiments of the subject matter and the functional operationsdescribed in this specification can be implemented in digital electroniccircuitry, in tangibly-embodied computer software or firmware, incomputer hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them. Embodiments of the subject matter described in thisspecification can be implemented as one or more computer programs, i.e.,one or more modules of computer program instructions encoded on atangible non-transitory program carrier for execution by, or to controlthe operation of, data processing apparatus. The computer storage mediumcan be a machine-readable storage device, a machine-readable storagesubstrate, a random or serial access memory device, or a combination ofone or more of them.

The term “data processing apparatus” refers to data processing hardwareand encompasses all kinds of apparatus, devices, and machines forprocessing data, including by way of example a programmable processor, acomputer, or multiple processors or computers. The apparatus can also beor further include special purpose logic circuitry, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application-specific integratedcircuit). The apparatus can optionally include, in addition to hardware,code that creates an execution environment for computer programs, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program, which may also be referred to or described as aprogram, software, a software application, a module, a software module,a script, or code, can be written in any form of programming language,including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program may, butneed not, correspond to a file in a file system. A program can be storedin a portion of a file that holds other programs or data, e.g., one ormore scripts stored in a markup language document, in a single filededicated to the program in question, or in multiple coordinated files,e.g., files that store one or more modules, sub-programs, or portions ofcode. A computer program can be deployed to be executed on one computeror on multiple computers that are located at one site or distributedacross multiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable computers executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Computers suitable for the execution of a computer program include, byway of example, can be based on general or special purposemicroprocessors or both, or any other kind of central processing unit.Generally, a central processing unit will receive instructions and datafrom a read-only memory or a random access memory or both. The essentialelements of a computer are a central processing unit for performing orexecuting instructions and one or more memory devices for storinginstructions and data. Generally, a computer will also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto-optical disks, or optical disks. However, a computer need nothave such devices. Moreover, a computer can be embedded in anotherdevice, e.g., a mobile telephone, a personal digital assistant (PDA), amobile audio or video player, a game console, a Global PositioningSystem (GPS) receiver, or a portable storage device, e.g., a universalserial bus (USB) flash drive, to name just a few.

Computer-readable media suitable for storing computer programinstructions and data include all forms of non-volatile memory, mediaand memory devices, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's device in response to requests received from the web browser.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back-end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front-end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described in this specification, or any combination of one ormore such back-end, middleware, or front-end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (LAN) and a widearea network (WAN), e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someembodiments, a server transmits data, e.g., an HTML page, to a userdevice, e.g., for purposes of displaying data to and receiving userinput from a user interacting with the user device, which acts as aclient. Data generated at the user device, e.g., a result of the userinteraction, can be received from the user device at the server.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinvention or on the scope of what may be claimed, but rather asdescriptions of features that may be specific to particular embodimentsof particular inventions. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or variation of a sub combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various system modulesand components in the embodiments described above should not beunderstood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Particular embodiments of the subject matter have been described. Otherembodiments are within the scope of the following claims. For example,the actions recited in the claims can be performed in a different orderand still achieve desirable results. As one example, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In some cases, multitasking and parallel processing may beadvantageous.

The invention claimed is:
 1. A computer-implemented method, comprising:receiving multiple search queries; identifying, for each search query ofthe received search queries, an entity associated with (i) the searchquery or (ii) a pair comprising the search query and an answer that asearch engine generates in response to the search query; after receivingthe search queries, receiving a voice query that includes a pronoun;identifying a plurality of acoustic parameters associated with thepronoun, wherein the identified plurality of acoustic parameterscomprise two or more of volume, pitch, frequency, duration between eachspoken word, and spoken duration of words or phrases; selecting, fromamong the identified entities associated with (i) the search queries or(ii) the pairs that each comprise a search query and an answer that asearch engine generates in response to the search query, a particularentity based at least on the identified plurality of acoustic parametersassociated with the pronoun comprising two or more of volume, pitch,frequency, duration between each spoken word, and spoken duration ofwords or phrases; modifying the voice query based at least on theselected entity; and obtaining an answer that the search enginegenerates in response to the modified search query.
 2. The method ofclaim 1, comprising: determining a stress score for the pronoun based atleast on the identified plurality of acoustic parameters.
 3. The methodof claim 2, wherein selecting, from among the identified entitiesassociated with (i) the search queries or (ii) the pairs that eachcomprise a search query and an answer that a search engine generates inresponse to the search query, a particular entity based at least on theidentified plurality of acoustic parameters comprising two or more ofvolume, pitch, frequency, duration between each spoken word, and spokenduration of words or phrases comprises: selecting the particular entitybased at least on the stress score for the pronoun.
 4. The method ofclaim 3, wherein selecting the particular entity based at least on thestress score for the pronoun comprises: determining whether the stressscore for the pronoun satisfies a predetermined threshold; and inresponse to determining that the stress score for the pronoun satisfiesthe predetermined threshold, selecting a most recently identifiedentity.
 5. The method of claim 3, wherein selecting the particularentity based at least on the stress score for the pronoun comprises:determining whether the stress score for the pronoun satisfies apredetermined threshold; and in response to determining that the stressscore for the pronoun does not satisfy the predetermined threshold,selecting an entity identified before a most recently identified entity.6. The method of claim 1, wherein selecting, from among the identifiedentities associated with (i) the search queries or (ii) the pairs thateach comprise a search query and an answer that a search enginegenerates in response to the search query, a particular entity based atleast on the identified plurality of acoustic parameters comprising twoor more of volume, pitch, frequency, duration between each spoken word,and spoken duration of words or phrases further comprises: selecting theparticular entity based on a gender that the pronoun references.
 7. Asystem comprising: one or more computers and one or more storage devicesstoring instructions that are operable, when executed by the one or morecomputers, to cause the one or more computers to perform operationscomprising: receiving multiple search queries; identifying, for eachsearch query of the received search queries, an entity associated with(i) the search query or (ii) a pair comprising the search query and ananswer that a search engine generates in response to the search query;after receiving the search queries, receiving a voice query thatincludes a pronoun; identifying a plurality of acoustic parametersassociated with the pronoun, wherein the identified plurality ofacoustic parameters include two or more of volume, pitch, frequency,duration between each spoken word, and spoken duration of words orphrases; selecting, from among the identified entities associated with(i) the search queries or (ii) the pairs that each comprise a searchquery and an answer that a search engine generates in response to thesearch query, a particular entity based at least on the identifiedplurality of acoustic parameters associated with the pronoun comprisingtwo or more of volume, pitch, frequency, duration between each spokenword, and spoken duration of words or phrases; modifying the voice querybased at least on the selected entity; and obtaining an answer that thesearch engine generates in response to the modified search query.
 8. Thesystem of claim 7, the operations comprising: determining a stress scorefor the pronoun based at least on the identified plurality of acousticparameters.
 9. The system of claim 8, wherein selecting, from among theidentified entities associated with (i) the search queries or (ii) thepairs that each comprise a search query and an answer that a searchengine generates in response to the search query, a particular entitybased at least on the identified plurality of acoustic parameterscomprising two or more of volume, pitch, frequency, duration betweeneach spoken word, and spoken duration of words or phrases comprises:selecting the particular entity based at least on the stress score forthe pronoun.
 10. The system of claim 9, wherein selecting the particularentity based at least on the stress score for the pronoun comprises:determining whether the stress score for the pronoun satisfies apredetermined threshold; and in response to determining that the stressscore for the pronoun satisfies the predetermined threshold, selecting amost recently identified entity.
 11. The system of claim 9, whereinselecting the particular entity based at least on the stress score forthe pronoun comprises: determining whether the stress score for thepronoun satisfies a predetermined threshold; and in response todetermining that the stress score for the pronoun does not satisfy thepredetermined threshold, selecting an entity identified before a mostrecently identified entity.
 12. A non-transitory computer-readablemedium storing software comprising instructions executable by one ormore computers which, upon such execution, cause the one or morecomputers to perform operations comprising: receiving multiple searchqueries; identifying, for each search query of the received searchqueries, an entity associated with (i) the search query or (ii) a paircomprising the search query and an answer that a search engine generatesin response to the search query; after receiving the search queries,receiving a voice query that includes a pronoun; identifying a pluralityof acoustic parameters associated with the pronoun, wherein theidentified plurality of acoustic parameters include two or more ofvolume, pitch, frequency, duration between each spoken word, and spokenduration of words or phrases; selecting, from among the identifiedentities associated with (i) the search queries or (ii) the pairs thateach comprise a search query and an answer that a search enginegenerates in response to the search query, a particular entity based atleast on the identified plurality of acoustic parameters associated withthe pronoun comprising two or more of volume, pitch, frequency, durationbetween each spoken word, and spoken duration of words or phrases;modifying the voice query based at least on the selected entity; andobtaining an answer that the search engine generates in response to themodified search query.
 13. The computer-readable medium of claim 12, theoperations comprising: determining a stress score for the pronoun basedat least on the identified plurality of acoustic parameters.
 14. Thecomputer-readable medium of claim 13, wherein selecting, from among theidentified entities associated with (i) the search queries or (ii) thepairs that each comprise a search query and an answer that a searchengine generates in response to the search query, a particular entitybased at least on the identified plurality of acoustic parameterscomprising two or more of volume, pitch, frequency, duration betweeneach spoken word, and spoken duration of words or phrases comprises:selecting the particular entity based at least on the stress score forthe pronoun.
 15. The computer-readable medium of claim 14, whereinselecting the particular entity based at least on the stress score forthe pronoun comprises: determining whether the stress score for thepronoun satisfies a predetermined threshold; and in response todetermining that the stress score for the pronoun satisfies thepredetermined threshold, selecting a most recently identified entity.16. The computer-readable medium of claim 14, wherein selecting theparticular entity based at least on the stress score for the pronouncomprises: determining whether the stress score for the pronounsatisfies a predetermined threshold; and in response to determining thatthe stress score for the pronoun does not satisfy the predeterminedthreshold, selecting an entity identified before a most recentlyidentified entity.
 17. The computer-readable medium of claim 12, whereinselecting, from among the identified entities associated with (i) thesearch queries or (ii) the pairs that each comprise a search query andan answer that a search engine generates in response to the searchquery, a particular entity based at least on the identified plurality ofacoustic parameters comprising two or more of volume, pitch, frequency,duration between each spoken word, and spoken duration of words orphrases further comprises: selecting the particular entity based on agender that the pronoun references.